Day 8 part 1

aoc.cabal

@@ -91,6 +91,8 @@ executable 8
     -- other-extensions:
     build-depends:    base ^>=4.18.2.1
                     , split
+                    , matrix
+                    , extra
     hs-source-dirs:   app
     default-language: GHC2021
 executable 9

app/8.hs

@@ -1,15 +1,72 @@
-{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE LambdaCase, MultiWayIf #-}
 module Main where
 
 import Data.Functor
+import Data.Matrix hiding (trace)
+import Data.List
+import Numeric.Extra
+import Debug.Trace
 
-parse = undefined
+data Pos = Pos { ch :: Char
+               , ma :: Bool
+               }
 
-solve1 = undefined
+instance Show Pos where
+  show (Pos '.' True) = show '#'
+  show (Pos ch _)     = show ch
+
+parse :: String -> Matrix Pos
+parse = fromLists . (((`Pos` False) <$>) <$>) . lines
+
+positionsOfChar :: Char -> Matrix Pos -> [(Int,Int)]
+positionsOfChar c s = zip [1..] (toLists s) >>= \(y,l) -> zip [1..] l >>= \(x,c') ->
+  if c == ch c' then pure (y,x) else mempty
+
+getMarked :: Matrix Pos -> [(Int,Int)]
+getMarked s = zip [1..] (toLists s) >>= \(y,l) -> zip [1..] l >>= \(x,c) ->
+  if ma c then pure (y,x) else mempty
+
+availableChars :: [Char]
+availableChars = ['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9']
+
+dist :: (Int,Int) -> (Int,Int) -> Float
+dist (y,x) (y',x') = sqrt $ intToFloat (y-y')^2 + intToFloat (x-x')^2
+
+line :: (Int,Int) -> (Int,Int) -> (Int,Int) -> Bool
+line (y1,x1) (y2,x2) (y3,x3) =
+  if | x2 == x1 && x3 == x2 -> True
+     | x2 == x1 || x3 == x2 || x1 == x3 -> False
+     | otherwise ->
+       ((y2-y1) `div` (x2-x1)) == ((y2-y3) `div` (x2-x3)) &&
+       ((y2-y1) `div` (x2-x1)) == ((y1-y3) `div` (x1-x3))
+
+combo :: Eq a => [a] -> [(a,a)]
+combo ps = [(a,b) | a <- ps, b <- ps, a /= b]
+
+
+getAntinodePos :: (Int,Int) -> [(Int,Int)] -> [(Int,Int)]
+getAntinodePos (i,j) ps =
+  let inbounds (y,x) = and [0 < y, y <= i, 0 < x, x <= j] in
+    nub $ [ c | (p@(y,x),p'@(y',x')) <- combo ps,
+                 c <- [(y + (y-y'),x+(x-x')),
+                       (y - (y-y'),x+(x-x')),
+                       (y + (y-y'),x-(x-x')),
+                       (y - (y-y'),x-(x-x'))],
+                 inbounds c,
+                 line c p p']
+
+
+mark :: Matrix Pos -> [(Int,Int)] -> Matrix Pos
+mark = foldr (\p@(y,x) s -> let c = getElem y x s in setElem (c {ma = True}) p s)
+
+solve1 :: Matrix Pos -> Int
+solve1 s = length . getMarked $
+  foldr (flip mark . getAntinodePos (nrows s, ncols s) . (`positionsOfChar` s)) s availableChars
 
 solve2 = undefined
 
 main :: IO ()
-main = readFile "inputs/8" <&> parse >>= \i ->
-       print (solve1 i) >>
-       print (solve2 i)
+main = readFile "inputs/8.example" <&> parse >>= \i ->
+       print (solve1 i)
+       -- >>
+       -- print (solve2 i)

inputs/8

@@ -0,0 +1,50 @@
+.......................V.........e...O............
+..........q.pj8...............................u...
+...................8..............................
+.............8.....6.................J....l....u..
+........................6................J..Z..B..
+......e.........E...........................O.J...
+......Jq..........................5...............
+...............E...........e.Q..5.f...............
+..............................Q..A.....f..B.....O.
+....V...................j.....Af..................
+............8......n..............l...f....Z7.....
+...............n..........4........A........BD....
+...........j...................Q..z.......R....l..
+N.........6....q.....3....n.........D...........Z.
+.............a.6..3.F........D..I.................
+.............03.................Q.......h...2.....
+......................A.u.......................m.
+.V........F......L.............5..........z.R....Z
+.......N....q.................n.......L.E.........
+..................M.........y.....................
+......N............................m.L..y........R
+.o....................L...........I...7..R........
+......o..........9..............2.......D.........
+..od.............y...........................I....
+d........3.....M...........E.............I........
+......X.W....................p.2.....7...z....s...
+V......o........M.....9.................G......7..
+.................M.....................h..0....m..
+.......d.......F......p.........s.h........z......
+..r..........Y.i................9............s....
+.....W..a.Y..........y.............p..............
+.....g.......r........w...........................
+....r.....b...............g........x.s.....h......
+....a.....d.......................................
+.....................S.......w.............1......
+..Y...............................H...............
+...b...........Y........................e..t...0.v
+..........i..........w.........9....T........v....
+.................U...........2....................
+.........S........t......T........................
+....................U..................Gt.........
+....U...S..........................P.....1.B......
+.r...X............w.......P.....x.j...............
+...W......x..b........g........F.....a............
+S.i.................................1.......H.....
+.......U......b......x.....X..........G.1.........
+...i....X....................P..4........H........
+.................................H................
+......W...................T4...g................v.
+..........................v........GP..4.....t....